IconEntry, set_icon_from_name: handle case when icon can not be found cleanly

Sugar crashes if the sugar theme has not been set (in sugar-session)
in the set_icon_from_name method since some if the requested icons
can not be found. Handle that case cleanly.

Signed-off-by: Simon Schampijer <simon@laptop.org>
Acked-by: Manuel Quiñones <manuq@laptop.org>

src/sugar3/graphics/iconentry.py

@@ -15,6 +15,8 @@
 # Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 # Boston, MA 02111-1307, USA.
 
+import logging
+
 from gi.repository import GObject
 from gi.repository import Gtk
 from gi.repository import Gdk
@@ -42,6 +44,10 @@ class IconEntry(Gtk.Entry):
         icon_info = icon_theme.lookup_icon(name,
                                            Gtk.IconSize.SMALL_TOOLBAR,
                                            0)
+        if not icon_info:
+            logging.warning('IconEntry set_icon_from_name: icon \'%s\' not '
+                            'found in the theme.', name)
+            return
 
         if icon_info.get_filename().endswith('.svg'):
             loader = _SVGLoader()